Not sure what to ask..

I had previously posted that I had pain on my left side, and spotting. I went to the obgyn today and she did an u/s she said I have a cysts on my left ovarie and the my lining in my uterus was a little thick. The cysts is 4 cm and it's clear fluid. (I had a d and c 3 months ago for a MMC) I've never had a cysts before, not sure what to expect. Also unclear as to why my lining is so thick. She is putting me on BC for one month and then said I can TTC again after... Has anyone had this issue? I feel so lost on this issue..